The present invention relates to a heavy duty tire having good rolling characteristics improved without lowering the wear resistance, more particularly to a heavy duty tire having a double layer tread composed of a cap rubber layer and a base rubber layer.
In heavy duty tires used for trucks and buses, in order to achieve both excellent wear resistance and low rolling resistance, it is known to form the tread thereof into a double layer structure composed of a cap rubber layer providing the outer surface of the tread and a base rubber layer disposed radially inward of the cap rubber layer, wherein a rubber having an excellent wear resistance is used in the cap rubber layer and a low heat-generating rubber having a low loss tangent is used in the base rubber layer. A tread having a three layer structure is also known as disclosed, for example, in JP 2005-35404 A.
From the viewpoint of low fuel cost, recently, further improvement in low rolling resistance is strongly demanded. However, even if the thickness of the cap rubber layer is simply decreased to increase the proportion of the low heat-generating base rubber, there arises a problem that the wear resistance is deteriorated. Therefore, it is difficult to simultaneously achieve high levels of wear resistance and rolling characteristics in tires including a double layered tread.
It is an object of the present invention to provide a heavy duty tire having both an improved low rolling resistance and an excellent wear resistance.
This and other objects of the present invention will become apparent from the description hereinafter.